Reinforced silicone resin film and method of preparing same

ABSTRACT

A method of preparing a reinforced silicone resin film, the method comprising the steps of impregnating a fiber reinforcement in a hydrosilylation-curable silicone composition comprising a silicone resin and a photoactivated hydrosilylation catalyst; and exposing the impregnated fiber reinforcement to radiation having a wavelength of from 150 to 800 nm at a dosage sufficient to cure the silicone resin; wherein the reinforced silicone resin film comprises from 10 to 99% (w/w) of the cured silicone resin and the film has a thickness of from 15 to 500 μm; and a reinforced silicone resin film prepared according to the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

None

FIELD OF THE INVENTION

The present invention relates to a method of preparing a reinforcedsilicone resin film and more particularly to a method comprisingimpregnating a fiber reinforcement in a hydrosilylation-curable siliconecomposition comprising a silicone resin and a photoactivatedhydrosilylation catalyst, and exposing the impregnated fiberreinforcement to radiation to cure the silicone resin. The presentinvention also relates to a reinforced silicone resin film preparedaccording to the method.

BACKGROUND OF THE INVENTION

Silicone resins are useful in a variety of applications by virtue oftheir unique combination of properties, including high thermalstability, good moisture resistance, excellent flexibility, high oxygenresistance, low dielectric constant, and high transparency. For example,silicone resins are widely used as protective or dielectric coatings inthe automotive, electronic, construction, appliance, and aerospaceindustries.

Although silicone resin coatings can be used to protect, insulate, orbond a variety of substrates, free standing silicone resin films havelimited utility due to low tear strength, high brittleness, low glasstransition temperature, and high coefficient of thermal expansion.Consequently, there is a need for free standing silicone resin filmshaving improved mechanical and thermal properties.

SUMMARY OF THE INVENTION

The present invention is directed to a method of preparing a reinforcedsilicone resin film, the method comprising the steps of:

-   -   impregnating a fiber reinforcement in a hydrosilylation-curable        silicone composition comprising a silicone resin and a        photoactivated hydrosilylation catalyst; and    -   exposing the impregnated fiber reinforcement to radiation having        a wavelength of from 150 to 800 nm at a dosage sufficient to        cure the silicone resin; wherein the reinforced silicone resin        film comprises from 10 to 99% (w/w) of the cured silicone resin        and the film has a thickness of from 15 to 500 μm.

The present invention is also directed to a reinforced silicone resinfilm prepared according to the aforementioned method.

The reinforced silicone resin film of the present invention has lowcoefficient of thermal expansion, high tensile strength, and highmodulus compared to an un-reinforced silicone resin film prepared fromthe same silicone composition. Also, although the reinforced andun-reinforced silicone resin films have comparable glass transitiontemperatures, the reinforced film exhibits a much smaller change inmodulus in the temperature range corresponding to the glass transition.

The reinforced silicone resin film of the present invention is useful inapplications requiring films having high thermal stability, flexibility,mechanical strength, and transparency. For example, the silicone resinfilm can be used as an integral component of flexible displays, solarcells, flexible electronic boards, touch screens, fire-resistantwallpaper, and impact-resistant windows. The film is also a suitablesubstrate for transparent or nontransparent electrodes.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “free of aliphatic unsaturation” means thehydrocarbyl or halogen-substituted hydrocarbyl group does not contain analiphatic carbon-carbon double bond or carbon-carbon triple bond. Also,the term “mol % of the groups R² in the silicone resin are alkenyl” isdefined as the ratio of the number of moles of silicon-bonded alkenylgroups in the silicone resin to the total number of moles of the groupsR² in the resin, multiplied by 100. Further, the term “mol % of thegroups R⁴ in the organohydrogen-polysioxane resin are organosilylalkyl”is defined as the ratio of the number of moles of silicon-bondedorganosilylalkyl groups in the silicone resin to the total number ofmoles of the groups R⁴ in the resin, multiplied by 100. Still further,the term “mol % of the groups R⁵ in the silicone resin are hydrogen” isdefined as the ratio of the number of moles of silicon-bonded hydrogenatoms in the silicone resin to the total number of moles of the groupsR⁵ in the resin, multiplied by 100.

A method of preparing a reinforced silicone resin film according to thepresent invention comprises the steps of:

-   -   impregnating a fiber reinforcement in a hydrosilylation-curable        silicone composition comprising a silicone resin and a        photoactivated hydrosilylation catalyst; and    -   exposing the impregnated fiber reinforcement to radiation having        a wavelength of from 150 to 800 nm at a dosage sufficient to        cure the silicone resin; wherein the reinforced silicone resin        film comprises from 10 to 99% (w/w) of the cured silicone resin        and the film has a thickness of from 15 to 500 μm.

In the first step of the method of preparing a reinforced silicone resinfilm, a fiber reinforcement is impregnated in a hydrosilylation-curablesilicone composition comprising a silicone resin and a photoactivatedhydrosilylation catalyst.

The hydrosilylation-curable silicone composition can be anyhydrosilylation-curable silicone composition comprising a silicone resinand a photoactivated hydrosilylation catalyst. Such compositionstypically contain a silicone resin having silicon-bonded alkenyl groupsor silicon-bonded hydrogen atoms, a cross-linking agent havingsilicon-bonded hydrogen atoms or silicon-bonded alkenyl groups capableof reacting with the silicon-bonded alkenyl groups or silicon-bondedhydrogen atoms in the resin, and a photoactivated hydrosilylationcatalyst. The silicone resin is typically a copolymer containing Tand/or Q siloxane units in combination with M and/or D siloxane units.Moreover, the silicone resin can be a rubber-modified silicone resin,described below for the fifth and sixth embodiments of the siliconecomposition.

According to a first embodiment, the hydrosilylation-curable siliconecomposition comprises (A) a silicone resin having the formula (R¹R²₂SiO_(1/2))_(w)(R² ₂SiO_(2/2))_(x) (R¹SiO_(3/2))_(y)(SiO_(4/2))_(z)(I),wherein R¹is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, R² is R¹ or alkenyl, wis from 0 to 0.8, x is from 0 to 0.6, y is from 0 to 0.99, z is from 0to 0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z)is from 0.01 to 0.8, provided the silicone resin has an average of atleast two silicon-bonded alkenyl groups per molecule; (B) anorganosilicon compound having an average of at least two silicon-bondedhydrogen atoms per molecule in an amount sufficient to cure the siliconeresin; and (C) a catalytic amount of a photoactivated hydrosilylationcatalyst.

Component (A) is at least one silicone resin having the formula (R¹R²₂SiO_(1/2))_(w) (R² ₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z) (I),wherein R¹is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, R² is R¹ or alkenyl, wis from 0 to 0.8, x is from 0 to 0.6, y is from 0 to 0.99, z is from 0to 0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z)is from 0.01 to 0.8, provided the silicone resin has an average of atleast two silicon-bonded alkenyl groups per molecule.

The hydrocarbyl and halogen-substituted hydrocarbyl groups representedby R¹ are free of aliphatic unsaturation and typically have from 1 to 10carbon atoms, alternatively from 1 to 6 carbon atoms. Acyclichydrocarbyl and halogen-substituted hydrocarbyl groups containing atleast 3 carbon atoms can have a branched or unbranched structure.Examples of hydrocarbyl groups represented by R¹ include, but are notlimited to, alkyl, such as methyl, ethyl, propyl, 1-methylethyl, butyl,1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl,1-methylbutyl, 1-ethylpropyl, 2-methylbutyl, 3-methylbutyl,1,2-dimethylpropyl, 2,2-dimethylpropyl, hexyl, heptyl, octyl, nonyl, anddecyl; cycloalkyl, such as cyclopentyl, cyclohexyl, andmethylcyclohexyl; aryl, such as phenyl and naphthyl; alkaryl, such astolyl and xylyl; and aralkyl, such as benzyl and phenethyl. Examples ofhalogen-substituted hydrocarbyl groups represented by R¹ include, butare not limited to, 3,3,3-trifluoropropyl, 3-chloropropyl, chlorophenyl,dichlorophenyl, 2,2,2-trifluoroethyl, 2,2,3,3-tetrafluoropropyl, and2,2,3,3,4,4,5,5-octafluoropentyl.

The alkenyl groups represented by R², which may be the same ordifferent, typically have from 2 to about 10 carbon atoms, alternativelyfrom 2 to 6 carbon atoms, and are exemplified by, but not limited to,vinyl, allyl, butenyl, hexenyl, and octenyl.

In the formula (I) of the silicone resin, the subscripts w, x, y, and zare mole fractions. The subscript w typically has a value of from 0 to0.8, alternatively from 0.02 to 0.75, alternatively from 0.05 to 0.3;the subscript x typically has a value of from 0 to 0.6, alternativelyfrom 0 to 0.45, alternatively from 0 to 0.25; the subscript y typicallyhas a value of from 0 to 0.99, alternatively from 0.25 to 0.8,alternatively from 0.5 to 0.8; the subscript z typically has a value offrom 0 to 0.35, alternatively from 0 to 0.25, alternatively from 0 to0.15. Also, the ratio y+z/(w+x+y+z) is typically from 0.2 to 0.99,alternatively from 0.5 to 0.95, alternatively from 0.65 to 0.9. Further,the ratio w+x/(w+x+y+z) is typically from 0.01 to 0.80, alternativelyfrom 0.05 to 0.5, alternatively from 0.1 to 0.35.

Typically at least 50 mol %, alternatively at least 65 mol %,alternatively at least 80 mol % of the groups R² in the silicone resinare alkenyl.

The silicone resin typically has a number-average molecular weight(M_(n)) of from 500 to 50,000, alternatively from 500 to 10,000,alternatively 1,000 to 3,000, where the molecular weight is determinedby gel permeation chromatography employing a low angle laser lightscattering detector, or a refractive index detector and silicone resin(MQ) standards.

The viscosity of the silicone resin at 25° C. is typically from 0.01 to100,000 Pa·s, alternatively from 0.1 to 10,000 Pa·s, alternatively from1 to 100 Pa·s.

The silicone resin typically contains less than 10% (w/w), alternativelyless than 5% (w/w), alternatively less than 2% (w/w), of silicon-bondedhydroxy groups, as determined by ²⁹Si NMR.

The silicone resin contains R¹SiO_(3/2) units (i.e., T units) and/orSiO_(4/2) units (i.e., Q units) in combination with R¹R² ₂SiO_(1/2)units (i.e., M units) and/or R² ₂SiO_(2/2) units (i.e., D units), whereR¹ and R² are as described and exemplified above. For example, thesilicone resin can be a DT resin, an MT resin, an MDT resin, a DTQresin, and MTQ resin, and MDTQ resin, a DQ resin, an MQ resin, a DTQresin, an MTQ resin, or an MDQ resin.

Examples of silicone resins include, but are not limited to, resinshaving the following formulae:(Vi₂MeSiO_(1/2))_(0.25)(PhSiO_(3/2))_(0.75),(ViMe₂SiO_(1/2))_(0.25)(PhSiO_(3/2))_(0.75),(ViMe₂SiO_(1/2))_(0.25)(MeSiO_(3/2))_(0.25)(PhSiO_(3/2))_(0.50),(ViMe₂SiO_(1/2))_(0.15)(PhSiO_(3/2))_(0.75) (SiO_(4/2))_(0.1,) and(Vi₂MeSiO_(1/2))_(0.15)(ViMe₂SiO_(1/2))_(0.1) (PhSiO_(3/2))_(0.75),where Me is methyl, Vi is vinyl, Ph is phenyl, and the numericalsubscripts outside the parenthesis denote mole fractions. Also, in thepreceding formulae, the sequence of units is unspecified.

Component (A) can be a single silicone resin or a mixture comprising twoor more different silicone resins, each as described above.

Methods of preparing silicone resins are well known in the art; many ofthese resins are commercially available. Silicone resins are typicallyprepared by cohydrolyzing the appropriate mixture of chlorosilaneprecursors in an organic solvent, such as toluene. For example, asilicone resin consisting essentially of R¹R² ₂SiO_(1/2) units andR¹SiO_(3/2) units can be prepared by cohydrolyzing a compound having theformula R¹R² ₂SiCl and a compound having the formula R¹ SiCl₃ intoluene, where R¹ and R² are as defined and exemplified above. Theaqueous hydrochloric acid and silicone hydrolyzate are separated and thehydrolyzate is washed with water to remove residual acid and heated inthe presence of a mild condensation catalyst to “body” the resin to therequisite viscosity. If desired, the resin can be further treated with acondensation catalyst in an organic solvent to reduce the content ofsilicon-bonded hydroxy groups. Alternatively, silanes containinghydrolysable groups other than chloro, such —Br, —I, —OCH₃, —OC(O)CH₃,—N(CH₃)₂, NHCOCH₃, and —SCH₃, can be utilized as starting materials inthe cohydrolysis reaction. The properties of the resin products dependon the types of silanes, the mole ratio of silanes, the degree ofcondensation, and the processing conditions.

Component (B) is at least one organosilicon compound having an averageof at least two silicon-bonded hydrogen atoms per molecule in an amountsufficient to cure the silicone resin of component (A).

The organosilicon compound has an average of at least two silicon-bondedhydrogen atoms per molecule, alternatively at least three silicon-bondedhydrogen atoms per molecule. It is generally understood thatcross-linking occurs when the sum of the average number of alkenylgroups per molecule in component (A) and the average number ofsilicon-bonded hydrogen atoms per molecule in component (B) is greaterthan four.

The organosilicon compound can be an organohydrogensilane or anorganohydrogensiloxane. The organohydrogensilane can be a monosilane,disilane, trisilane, or polysilane. Similarly, theorganohydrogensiloxane can be a disiloxane, trisiloxane, orpolysiloxane. The structure of the organosilicon compound can be linear,branched, cyclic, or resinous. Cyclosilanes and cyclosiloxanes typicallyhave from 3 to 12 silicon atoms, alternatively from 3 to 10 siliconatoms, alternatively from 3 to 4 silicon atoms. In acyclic polysilanesand polysiloxanes, the silicon-bonded hydrogen atoms can be located atterminal, pendant, or at both terminal and pendant positions.

Examples of organohydrogensilanes include, but are not limited to,diphenylsilane, 2-chloroethylsilane, bis[(p-dimethylsilyl)phenyl]ether,1,4-dimethyldisilylethane, 1,3,5-tris(dimethylsilyl)benzene,1,3,5-trimethyl-1,3,5-trisilane, poly(methylsilylene)phenylene, andpoly(methylsilylene)methylene.

The organohydrogensilane can also have the formula HR¹ ₂Si—R³—SiR¹ ₂H,wherein R¹ is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, and R³ is ahydrocarbylene group free of aliphatic unsaturation having a formulaselected from:

wherein g is from 1 to 6. The hydrocarbyl and halogen-substitutedhydrocarbyl groups represented by R¹ are as defined and exemplifiedabove for the silicone resin of component (A).

Examples of organohydrogensilanes having the formula HR¹ ₂Si—R³—SiR¹ ₂H,wherein R¹ and R³ are as described and exemplified above include, butare not limited to, silanes having the following formulae:

Examples of organohydrogensiloxanes include, but are not limited to,1,1,3,3-tetramethyldisiloxane, 1,1,3,3-tetraphenyldisiloxane,phenyltris(dimethylsiloxy)silane, 1,3,5-trimethylcyclotrisiloxane, atrimethylsiloxy-terminated poly(methylhydrogensiloxane), atrimethylsiloxy-terminatedpoly(dimethylsiloxane/methylhydrogensiloxane), adimethylhydrogensiloxy-terminated poly(methylhydrogensiloxane), and aresin consisting essentially of HMe₂SiO_(1/2) units, Me₃SiO_(1/2) units,and SiO_(4/2) units, wherein Me is methyl.

The organohydrogensiloxane can also be an organohydrogenpolysiloxaneresin having he formula (R¹R⁴ ₂SiO_(1/2))_(w)(R⁴₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z)(II), wherein R¹ is C₁ toC₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both freeof aliphatic unsaturation, R⁴ is R¹ or an organosilylalkyl group havingat least one silicon-bonded hydrogen atom, w is from 0 to 0.8, x is from0 to 0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1,y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided at least 50 mol % of the groups R⁴ are organosilylalkyl.

The hydrocarbyl and halogen-substituted hydrocarbyl groups representedby R¹ are as described and exemplified above for the silicone resin ofcomponent (A). Examples of organosilylalkyl groups represented by R⁴include, but are not limited to, groups having the following formulae:

where Me is methyl, Ph is phenyl, and the subscript n has a value offrom 2 to 10.

In the formula (II) of the organohydrogenpolysiloxane resin, thesubscripts w, x, y, and z are mole fractions. The subscript w typicallyhas a value of from 0 to 0.8, alternatively from 0.02 to 0.75,alternatively from 0.05 to 0.3; the subscript x typically has a value offrom 0 to 0.6, alternatively from 0 to 0.45, alternatively from 0 to0.25; the subscript y typically has a value of from 0 to 0.99,alternatively from 0.25 to 0.8, alternatively from 0.5 to 0.8; thesubscript z typically has a value of from 0 to 0.35, alternatively from0 to 0.25, alternatively from 0 to 0.15. Also, the ratio y+z/(w+x+y+z)is typically from 0.2 to 0.99, alternatively from 0.5 to 0.95,alternatively from 0.65 to 0.9. Further, the ratio w+x/(w+x+y+z) istypically from 0.01 to 0.80, alternatively from 0.05 to 0.5,alternatively from 0.1 to 0.35.

Typically, at least 50 mol %, alternatively at least 65 mol %,alternatively at least 80 mol % of the groups R⁴ in theorganohydrogenpolysiloxane resin are organosilylalkyl groups having atleast one silicon-bonded hydrogen atom.

The organohydrogenpolysiloxane resin typically has a number-averagemolecular weight (M_(n)) of from 500 to 50,000, alternatively from 500to 10,000, alternatively 1,000 to 3,000, where the molecular weight isdetermined by gel permeation chromatography employing a low angle laserlight scattering detector, or a refractive index detector and siliconeresin (MQ) standards.

The organohydrogenpolysiloxane resin typically contains less than 10%(w/w), alternatively less than 5% (w/w), alternatively less than 2%(w/w), of silicon-bonded hydroxy groups, as determined by ²⁹Si NMR.

The organohydrogenpolysiloxane resin contains R¹SiO_(3/2) units (i.e., Tunits) and/or SiO_(4/2) units (i.e., Q units) in combination with R¹R⁴₂SiO_(1/2) units (i.e., M units) and/or R⁴ ₂SiO_(2/2) units (i.e., Dunits), where R¹ and R⁴ are as described and exemplified above. Forexample, the organohydrogenpolysiloxane resin can be a DT resin, an MTresin, an MDT resin, a DTQ resin, and MTQ resin, and MDTQ resin, a DQresin, an MQ resin, a DTQ resin, an MTQ resin, or an MDQ resin.

Examples of organohydrogenpolysiloxane resins include, but are notlimited to, resins having the following formulae:

-   ((HMe₂SiC₆H₄SiMe₂CH₂CH₂)₂MeSiO_(1/2))_(0.12)(PhSiO_(3/2))_(0.88,)-   ((HMehd 2SiC₆H₄SiMe₂CH₂CH₂)₂MeSiO_(1/2))_(0.17)(PhSiO_(3/2))_(0.83),-   ((HMe₂SiC₆H₄SiMe₂CH₂CH₂)₂MeSiO_(1/2))_(0.17)(MeSiO_(3/2))_(0.17)(PhSiO_(3/2))_(0.66),-   ((HMe₂SiC₆H₄SiMe₂CH₂CH₂)₂MeSiO_(1/2))_(0.15)(PhSiO_(3/2))_(0.75)(SiO_(4/2))_(0.10,)    and-   ((HMe₂SiC₆H₄SiMe₂CH₂CH₂)₂MeSiO_(1/2))_(0.08)((HMe₂SiC₆H₄SiMe₂CH₂CH₂)    Me₂SiO_(1/2))_(0.06) (PhSiO_(3/2))_(0.86), where Me is methyl, Ph is    phenyl, C₆H₄ denotes a para-phenylene group, and the numerical    subscripts outside the parenthesis denote mole fractions. Also, in    the preceding formulae, the sequence of units is unspecified.

Component (B) can be a single organosilicon compound or a mixturecomprising two or more different organosilicon compounds, each asdescribed above. For example, component (B) can be a singleorganohydrogensilane, a mixture of two different organohydrogensilanes,a single organohydrogensiloxane, a mixture of two differentorganohydrogensiloxanes, or a mixture of an organohydrogensilane and anorganohydrogensiloxane. In particular, component (B) can be a mixturecomprising at least 0.5% (w/w), alternatively at least 50% (w/w),alternatively at least 75% (w/w), based on the total weight of component(B), of the organohydrogenpolysiloxane resin having the formula (II),and an organohydrogensilane and/or organohydrogensiloxane, the latterdifferent from the organohydrogenpolysiloxane resin.

The concentration of component (B) is sufficient to cure (cross-link)the silicone resin of component (A). The exact amount of component (B)depends on the desired extent of cure, which generally increases as theratio of the number of moles of silicon-bonded hydrogen atoms incomponent (B) to the number of moles of alkenyl groups in component (A)increases. The concentration of component (B) is typically sufficient toprovide from 0.4 to 2 moles of silicon-bonded hydrogen atoms,alternatively from 0.8 to 1.5 moles of silicon-bonded hydrogen atoms,alternatively from 0.9 to 1.1 moles of silicon-bonded hydrogen atoms,per mole of alkenyl groups in component (A).

Methods of preparing organosilicon compounds containing silicon-bondedhydrogen atoms are well known in the art. For example,organohydrogensilanes can be prepared by reaction of Grignard reagentswith alkyl or aryl halides. In particular, organohydrogensilanes havingthe formula HR¹ ₂Si—R³-SiR¹ ₂H can be prepared by treating an aryldihalide having the formula R³X₂ with magnesium in ether to produce thecorresponding Grignard reagent and then treating the Grignard reagentwith a chlorosilane having the formula HR¹ ₂SiCl, where R¹ and R³ are asdescribed and exemplified above.

Methods of preparing organohydrogensiloxanes, such as the hydrolysis andcondensation of organohalosilanes, are also well known in the art.

In addition, the organohydrogenpolysiloxane resin having the formula(II) can be prepared by reacting (a) a silicone resin having the formula(R¹R² ₂SiO_(1/2))_(w)(R² ₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z)(I) with (b) an organosilicon compoundhaving an average of from two to four silicon-bonded hydrogen atoms permolecule and a molecular weight less than 1,000, in the presence of (c)a hydrosilylation catalyst and, optionally, (d) an organic solvent,wherein R¹is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, R² is R¹ or alkenyl, wis from 0 to 0.8, x is from 0 to 0.6, y is from 0 to 0.99, z is from 0to 0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z)is from 0.01 to 0.8, provided the silicone resin (a) has an average ofat least two silicon-bonded alkenyl groups per molecule, and the moleratio of silicon-bonded hydrogen atoms in (b) to alkenyl groups in (a)is from 1.5 to 5.

Silicone resin (a) is as described and exemplified above for component(A) of the silicone composition. Silicone resin (a) can be the same asor different than the silicone resin used as component (A) in thehydrosilylation-curable silicone composition.

Organosilicon compound (b) is at least one organosilicon compound havingan average of from two to four silicon-bonded hydrogen atoms permolecule. Alternatively, the organosilicon compound has an average offrom two to three silicon-bonded hydrogen atoms per molecule. Theorganosilicon compound typically has a molecular weight less than 1,000,alternatively less than 750, alternatively less than 500. Thesilicon-bonded organic groups in the organosilicon compound are selectedfrom hydrocarbyl and halogen-substituted hydrocarbyl groups, both freeof aliphatic unsaturation, which are as described and exemplified abovefor R¹ in the formula of the silicone resin of component (A).

Organosilicon compound (b) can be an organohydrogensilane or anorganohydrogensiloxane. The organohydrogensilane can be a monosilane,disilane, trisilane, or polysilane. Similarly, theorganohydrogensiloxane can be a disiloxane, trisiloxane, orpolysiloxane. The structure of the organosilicon compound can be linear,branched, or cyclic. Cyclosilanes and cyclosiloxanes typically have from3 to 12 silicon atoms, alternatively from 3 to 10 silicon atoms,alternatively from 3 to 4 silicon atoms. In acyclic polysilanes andpolysiloxanes, the silicon-bonded hydrogen atoms can be located atterminal, pendant, or at both terminal and pendant positions.

Examples of organohydrogensilanes include, but are not limited to,diphenylsilane, 2-chloroethylsilane, bis[(p-dimethylsilyl)phenyl]ether,1,4-dimethyldisilylethane, 1,3,5-tris(dimethylsilyl)benzene, and1,3,5-trimethyl-1,3,5-trisilane. The organohydrogensilane can also havethe formula HR¹ ₂Si—R³—SiR¹ ₂H, wherein R¹ and R³ are as described andexemplified above.

Examples of organohydrogensiloxanes include, but are not limited to,1,1,3,3-tetramethyldisiloxane, 1,1,3,3-tetraphenyldisiloxane,phenyltris(dimethylsiloxy)silane, and 1,3,5-trimethylcyclotrisiloxane.

Organosilicon compound (b) can be a single organosilicon compound or amixture comprising two or more different organosilicon compounds, eachas described above. For example, component (B) can be a singleorganohydrogensilane, a mixture of two different organohydrogensilanes,a single organohydrogensiloxane, a mixture of two differentorganohydrogensiloxanes, or a mixture of an organohydrogensilane and anorganohydrogensiloxane.

Methods of preparing organohydrogensilanes, such as the reaction ofGrignard reagents with alkyl or aryl halides, described above, are wellknown in the art. Similarly, methods of preparingorganohydrogensiloxanes, such as the hydrolysis and condensation oforganohalosilanes, are well known in the art.

Hydrosilylation catalyst (c) can be any of the well-knownhydrosilylation catalysts comprising a platinum group metal (i.e.,platinum, rhodium, ruthenium, palladium, osmium and iridium) or acompound containing a platinum group metal. Preferably, the platinumgroup metal is platinum, based on its high activity in hydrosilylationreactions.

Hydrosilylation catalysts include the complexes of chloroplatinic acidand certain vinyl-containing organosiloxanes disclosed by Willing inU.S. Pat. No. 3,419,593, which is hereby incorporated by reference. Acatalyst of this type is the reaction product of chloroplatinic acid and1,3-diethenyl-1,1,3,3-tetramethyldisiloxane.

The hydrosilylation catalyst can also be a supported hydrosilylationcatalyst comprising a solid support having a platinum group metal on thesurface thereof. A supported catalyst can be conveniently separated fromthe organohydrogenpolysiloxane resin product, for example, by filteringthe reaction mixture. Examples of supported catalysts include, but arenot limited to, platinum on carbon, palladium on carbon, ruthenium oncarbon, rhodium on carbon, platinum on silica, palladium on silica,platinum on alumina, palladium on alumina, and ruthenium on alumina.

Organic solvent (d) is at least one organic solvent. The organic solventcan be any aprotic or dipolar aprotic organic solvent that does notreact with silicone resin (a), organosilicon compound (b), or theorganohydrogenpolysiloxane resin under the conditions of the presentmethod, and is miscible with components (a), (b), and theorganohydrogenpolysiloxane resin.

Examples of organic solvents include, but are not limited to, saturatedaliphatic hydrocarbons such as n-pentane, hexane, n-heptane, isooctaneand dodecane; cycloaliphatic hydrocarbons such as cyclopentane andcyclohexane; aromatic hydrocarbons such as benzene, toluene, xylene andmesitylene; cyclic ethers such as tetrahydrofuran (THF) and dioxane;ketones such as methyl isobutyl ketone (MIBK); halogenated alkanes suchas trichloroethane; and halogenated aromatic hydrocarbons such asbromobenzene and chlorobenzene. Organic solvent (d) can be a singleorganic solvent or a mixture comprising two or more different organicsolvents, each as described above.

The reaction can be carried out in any standard reactor suitable forhydrosilylation reactions. Suitable reactors include glass andTeflon-lined glass reactors. Preferably, the reactor is equipped with ameans of agitation, such as stirring. Also, preferably, the reaction iscarried out in an inert atmosphere, such as nitrogen or argon, in theabsence of moisture.

The silicone resin, organosilicon compound, hydrosilylation catalyst,and, optionally, organic solvent, can be combined in any order.Typically, organosilicon compound (b) and hydrosilylation catalyst (c)are combined before the introduction of the silicone resin (a) and,optionally, organic solvent (d).

The reaction is typically carried out at a temperature of from 0 to 150°C., alternatively from room temperature (˜23±2° C.) to 115° C. When thetemperature is less than 0° C., the rate of reaction is typically veryslow.

The reaction time depends on several factors, such as the structures ofthe silicone resin and the organosilicon compound, and the temperature.The time of reaction is typically from 1 to 24 h at a temperature offrom room temperature (˜23±2° C.) to 150 ° C. The optimum reaction timecan be determined by routine experimentation using the methods set forthin the Examples section below.

The mole ratio of silicon-bonded hydrogen atoms in organosiliconcompound (b) to alkenyl groups in silicone resin (a) is typically from1.5 to 5, alternatively from 1.75 to 3, alternatively from 2 to 2.5.

The concentration of hydrosilylation catalyst (c) is sufficient tocatalyze the addition reaction of silicone resin (a) with organosiliconcompound (b). Typically, the concentration of hydrosilylation catalyst(c) is sufficient to provide from 0.1 to 1000 ppm of a platinum groupmetal, alternatively from 1 to 500 ppm of a platinum group metal,alternatively from 5 to 150 ppm of a platinum group metal, based on thecombined weight of silicone resin (a) and organosilicon compound (b).The rate of reaction is very slow below 0.1 ppm of platinum group metal.The use of more than 1000 ppm of platinum group metal results in noappreciable increase in reaction rate, and is therefore uneconomical.

The concentration of organic solvent (d) is typically from 0 to 99%(w/w), alternatively from 30 to 80% (w/w), alternatively from 45 to 60%(w/w), based on the total weight of the reaction mixture.

The organohydrogenpolysiloxane resin can be used without isolation orpurification in the first embodiment of the hydrosilylation-curablesilicone composition or the resin can be separated from most of thesolvent by conventional methods of evaporation. For example, thereaction mixture can be heated under reduced pressure. Moreover, whenthe hydrosilylation catalyst used to prepare theorganohydrogenpolysiloxane resin is a supported catalyst, describedabove, the resin can be readily separated from the hydrosilylationcatalyst by filtering the reaction mixture.

Component (C) of the hydrosilylation-curable silicone composition is atleast one photoactivated hydrosilylation catalyst. The photoactivatedhydrosilylation catalyst can be any hydrosilylation catalyst capable ofcatalyzing the hydrosilylation of component (A) with component (B) uponexposure to radiation having a wavelength of from 150 to 800 nm. Thephotoactivated hydrosilylation catalyst can be any of the well-knownhydrosilylation catalysts comprising a platinum group metal or acompound containing a platinum group metal. The platinum group metalsinclude platinum, rhodium, ruthenium, palladium, osmium and iridium.Typically, the platinum group metal is platinum, based on its highactivity in hydrosilylation reactions. The suitability of particularphotoactivated hydrosilylation catalyst for use in the siliconecomposition of the present invention can be readily determined byroutine experimentation using the methods in the Examples section below.

Examples of photoactivated hydrosilylation catalysts include, but arenot limited to, platinum(II) β-diketonate complexes such as platinum(II)bis(2,4-pentanedioate), platinum(II) bis(2,4-hexanedioate), platinum(II)bis(2,4-heptanedioate), platinum(II) bis(1-phenyl-1,3-butanedioate,platinum(II) bis(1,3-diphenyl-1,3-propanedioate), platinum(II)bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedioate);(η-cyclopentadienyl)trialkylplatinum complexes, such as(Cp)trimethylplatinum, (Cp)ethyldimethylplatinum, (Cp)triethylplatinum,(chloro-Cp)trimethylplatinum, and (trimethylsilyl-Cp)trimethylplatinum,where Cp represents cyclopentadienyl; triazene oxide-transition metalcomplexes, such as Pt[C₆H₅NNNOCH₃]₄, Pt[p-CN-C₆H₄NNNOC₆H₁₁]₄,Pt[p-H₃COC₆H₄NNNOC₆H₁₁]₄, Pt[p-CH₃(CH₂)_(x)-C₆H₄NNNOCH₃]₄,1,5-cyclooctadiene.Pt[p-CN-C₆H₄NNNOC₆H₁₁]₂,1,5-cyclooctadiene.Pt[p-CH₃O-C₆H₄NNNOCH₃]₂,[(C₆H₅)₃P]₃Rh[p-CN-C₆H₄NNNOC₆H₁₁], and Pd[p-CH₃(CH₂)_(x)—C₆H₄NNOCH₃]₂,where x is 1, 3, 5, 11, or 17; (η-diolefin)(σ-aryl)platinum complexes,such as (η⁴-1,5-cyclooctadienyl)diphenylplatinum,η⁴-1,3,5,7-cyclooctatetraenyl)diphenylplatinum,(η⁴-2,5-norboradienyl)diphenylplatinum,(η⁴-1,5-cyclooctadienyl)bis-(4-dimethylaminophenyl)platinum,(η⁴-1,5-cyclooctadienyl)bis-(4-acetylphenyl)platinum, and(η⁴-1,5-cyclooctadienyl)bis-(4-trifluormethylphenyl)platinum.Preferably, the photoactivated hydrosilylation catalyst is a Pt(II)β-diketonate complex and more preferably the catalyst is platinum(II)bis(2,4-pentanedioate).

Component (C) can be a single photoactivated hydrosilylation catalyst ora mixture comprising two or more different photoactivatedhydrosilylation catalysts.

The concentration of component (C) is sufficient to catalyze theaddition reaction of component (A) with (B) upon exposure to radiationas described in the method below. The concentration of component (C) issufficient to provide typically from 0.1 to 1000 ppm of platinum groupmetal, alternatively from 0.5 to 100 ppm of platinum group metal,alternatively from 1 to 25 ppm of platinum group metal, based on thecombined weight of components (A) and (B). The rate of cure is very slowbelow 1 ppm of platinum group metal. The use of more than 100 ppm ofplatinum group metal results in no appreciable increase in cure rate,and is therefore uneconomical.

Methods of preparing photoactivated hydrosilylation catalysts are wellknown in the art. For example, methods of preparing platinum(II)β-diketonates are reported by Guo et al. (Chemistry of Materials, 1998,10, 531-536). Methods of preparing (η-cyclopentadienyl)-trialkylplatinumcomplexes and are disclosed in U.S. Pat. No. 4,510,094. Methods ofpreparing triazene oxide-transition metal complexes are disclosed inU.S. Pat. No. 5,496,961. And, methods of preparing(η-diolefin)(σ-aryl)platinum complexes are taught in U.S. Pat. No.4,530,879.

According to a second embodiment, the hydrosilylation-curable siliconecomposition comprises (A′) a silicone resin having the formula (R¹R⁵₂SiO_(1/2))_(w) (R⁵₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z)(III), wherein R¹is C₁ toC₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both freeof aliphatic unsaturation, R⁵ is R¹ or —H, w is from 0 to 0.8, x is from0 to 0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1,y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided the silicone resin has an average of at least twosilicon-bonded hydrogen atoms per molecule; (B′) an organosiliconcompound having an average of at least two silicon-bonded alkenyl groupsper molecule in an amount sufficient to cure the silicone resin; and (C)a catalytic amount of a photoactivated hydrosilylation catalyst.

Component (A′) is at least one silicone resin having the formula (R¹R⁵₂SiO_(1/2))_(w) (R⁵ ₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z)(III), wherein R¹is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀halogen-substituted hydrocarbyl, both free of aliphatic unsaturation, R⁵is R¹ or —H, w is from 0 to 0.8, x is from 0 to 0.6, y is from 0 to0.99, z is from 0 to 0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99,and w+x/(w+x+y+z) is from 0.01 to 0.8, provided the silicone resin hasan average of at least two silicon-bonded hydrogen atoms per molecule.In the formula (III), R¹, w, x, y, z, y+z/(w+x+y+z), and w+x/(w+x+y+z)are as described and exemplified above for the silicone resin having theformula (I).

Typically at least 50 mol %, alternatively at least 65 mol %,alternatively at least 80 mol % of the groups R⁵ in the silicone resinare hydrogen. The silicone resin typically has a number-averagemolecular weight (M_(n)) of from 500 to 50,000, alternatively from 500to 10,000, alternatively 1,000 to 3,000, where the molecular weight isdetermined by gel permeation chromatography employing a low angle laserlight scattering detector, or a refractive index detector and siliconeresin (MQ) standards.

The viscosity of the silicone resin at 25° C. is typically from 0.01 to100,000 Pa·s, alternatively from 0.1 to 10,000 Pa·s, alternatively from1 to 100 Pa·s.

The silicone resin typically contains less than 10% (w/w), alternativelyless than 5% (w/w), alternatively less than 2% (w/w), of silicon-bondedhydroxy groups, as determined by ²⁹Si NMR.

The silicone resin contains R⁵SiO_(3/2) units (i.e., T units) and/orSiO_(4/2) units (i.e., Q units) in combination with R¹R⁵ ₂SiO_(1/2)units (i.e., M units) and/or R⁵ ₂SiO_(2/2) units (i.e., D units). Forexample, the silicone resin can be a DT resin, an MT resin, an MDTresin, a DTQ resin, and MTQ resin, and MDTQ resin, a DQ resin, an MQresin, a DTQ resin, an MTQ resin, or an MDQ resin.

Examples of silicone resins suitable for use as component (A′) include,but are not limited to, resins having the following formulae:(HMe₂SiO_(1/2))_(0.25)(PhSiO_(3/2))_(0.75),(HMeSiO_(2/2))_(0.3)(PhSiO_(3/2))_(0.6)(MeSiO_(3/2))_(0.1), and(Me₃SiO_(1/2))_(0.1)(H₂SiO_(2/2))_(0.1)(MeSiO_(3/2))_(0.4)(PhSiO_(3/2))_(0.4,)where Me is methyl, Ph is phenyl, and the numerical subscripts outsidethe parenthesis denote mole fractions. Also, in the preceding formulae,the sequence of units is unspecified.

Component (A′) can be a single silicone resin or a mixture comprisingtwo or more different silicone resins, each as described above.

Methods of preparing silicone resins containing silicon-bonded hydrogenatoms are well known in the art; many of these resins are commerciallyavailable. Silicone resins are typically prepared by cohydrolyzing theappropriate mixture of chlorosilane precursors in an organic solvent,such as toluene. For example, a silicone resin consisting essentially ofR¹R⁵ ₂SiO_(1/2) units and R⁵SiO_(3/2) units can be prepared bycohydrolyzing a compound having the formula R¹R⁵ ₂SiCl and a compoundhaving the formula R⁵SiCl₃ in toluene, where R¹ and R⁵ are as describedand exemplified above. The aqueous hydrochloric acid and siliconehydrolyzate are separated and the hydrolyzate is washed with water toremove residual acid and heated in the presence of a mild non-basiccondensation catalyst to “body” the resin to the requisite viscosity. Ifdesired, the resin can be further treated with a non-basic condensationcatalyst in an organic solvent to reduce the content of silicon-bondedhydroxy groups. Alternatively, silanes containing hydrolysable groupsother than chloro, such —Br, —I, —OCH₃, —OC(O)CH₃, —N(CH₃)₂, NHCOCH₃,and —SCH₃, can be utilized as starting materials in the cohydrolysisreaction. The properties of the resin products depend on the types ofsilanes, the mole ratio of silanes, the degree of condensation, and theprocessing conditions.

Component (B′) is at least one organosilicon compound having an averageof at least two silicon-bonded alkenyl groups per molecule in an amountsufficient to cure the silicone resin of component (A′).

The organosilicon compound contains an average of at least twosilicon-bonded alkenyl groups per molecule, alternatively at least threesilicon-bonded alkenyl groups per molecule. It is generally understoodthat cross-linking occurs when the sum of the average number ofsilicon-bonded hydrogen atoms per molecule in component (A′) and theaverage number of silicon-bonded alkenyl groups per molecule incomponent (B′) is greater than four.

The organosilicon compound can be an organosilane or an organosiloxane.The organosilane can be a monosilane, disilane, trisilane, orpolysilane. Similarly, the organosiloxane can be a disiloxane,trisiloxane, or polysiloxane. The structure of the organosiliconcompound can be linear, branched, cyclic, or resinous. Cyclosilanes andcyclosiloxanes typically have from 3 to 12 silicon atoms, alternativelyfrom 3 to 10 silicon atoms, alternatively from 3 to 4 silicon atoms. Inacyclic polysilanes and polysiloxanes, the silicon-bonded alkenyl groupscan be located at terminal, pendant, or at both terminal and pendantpositions.

Examples of organosilanes suitable for use as component (B′) include,but are not limited to, silanes having the following formulae: Vi₄Si,PhSiVi₃, MeSiVi₃, PhMeSiVi₂, Ph₂SiVi₂, and PhSi(CH₂CH═CH₂)₃, where Me ismethyl, Ph is phenyl, and Vi is vinyl.

Examples of organosiloxanes suitable for use as component (B′) include,but are not limited to, siloxanes having the following formulae:

-   PhSi(OSiMe₂H)₃, Si(OSiMe₂H)₄, MeSi(OSiMe₂H)₃, and Ph₂Si(OSiMe₂H)₂,    where Me is methyl, and Ph is phenyl.

Component (B′) can be a single organosilicon compound or a mixturecomprising two or more different organosilicon compounds, each asdescribed above. For example component (B′) can be a singleorganosilane, a mixture of two different organosilanes, a singleorganosiloxane, a mixture of two different organosiloxanes, or a mixtureof an organosilane and an organosiloxane.

The concentration of component (B′) is sufficient to cure (cross-link)the silicone resin of component (A′). The exact amount of component (B′)depends on the desired extent of cure, which generally increases as theratio of the number of moles of silicon-bonded alkenyl groups incomponent (B′) to the number of moles of silicon-bonded hydrogen atomsin component (A′) increases. The concentration of component (B′) istypically sufficient to provide from 0.4 to 2 moles of silicon-bondedalkenyl groups, alternatively from 0.8 to 1.5 moles of silicon-bondedalkenyl groups, alternatively from 0.9 to 1.1 moles of silicon-bondedalkenyl groups, per mole of silicon-bonded hydrogen atoms in component(A′).

Methods of preparing organosilanes and organosiloxanes containingsilicon-bonded alkenyl groups are well known in the art; many of thesecompounds are commercially available.

Component (C) of the second embodiment of the silicone composition is asdescribed and exemplified above for component (C) of the firstembodiment.

According to a third embodiment, the hydrosilylation-curable siliconecomposition comprises (A) a silicone resin having the formula (R¹R²₂SiO_(1/2))_(w)(R² ₂SiO_(2/2))_(x) (R¹ SiO_(3/2))_(y)(SiO_(4/2))_(z)(I);(B) an organosilicon compound having an average of at least twosilicon-bonded hydrogen atoms per molecule in an amount sufficient tocure the silicone resin; (C) a catalytic amount of a photoactivatedhydrosilylation catalyst; and (D) a silicone rubber having a formulaselected from (i) R¹R² ₂SiO(R² ₂SiO)_(a)SiR² ₂R¹ (IV) and (ii) R⁵R¹₂SiO(R¹R⁵SiO)_(b)SiR¹ ₂R⁵ (V); wherein R¹ is C₁ to C₁₀ hydrocarbyl or C₁to C₁₀ halogen-substituted hydrocarbyl, both free of aliphaticunsaturation, R² is R¹ or alkenyl, R⁵ is R¹ or —H, subscripts a and beach have a value of from 1 to 4, w is from 0 to 0.8, x is from 0 to0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1, y+z/(w+x+y+z)is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to 0.8, provided thesilicone resin and the silicone rubber (D)(i) each have an average of atleast two silicon-bonded alkenyl groups per molecule, the siliconerubber (D)(ii) has an average of at least two silicon-bonded hydrogenatoms per molecule, and the mole ratio of silicon-bonded alkenyl groupsor silicon-bonded hydrogen atoms in the silicone rubber (D) tosilicon-bonded alkenyl groups in the silicone resin (A) is from 0.01 to0.5.

Components (A), (B), and (C) of the third embodiment of the siliconecomposition are as described and exemplified above for the firstembodiment.

The concentration of component (B) is sufficient to cure (cross-link)the silicone resin of component (A). When component (D) is (D)(i), theconcentration of component (B) is such that the ratio of the number ofmoles of silicon-bonded hydrogen atoms in component (B) to the sum ofthe number of moles of silicon-bonded alkenyl groups in component (A)and component (D)(i) is typically from 0.4 to 2, alternatively from 0.8to 1.5, alternatively from 0.9 to 1.1. Furthermore, when component (D)is (D)(ii), the concentration of component (B) is such that the ratio ofthe sum of the number of moles of silicon-bonded hydrogen atoms incomponent (B) and component (D)(ii) to the number of moles ofsilicon-bonded alkenyl groups in component (A) is typically from 0.4 to2, alternatively from 0.8 to 1.5, alternatively from 0.9 to 1.1.

Component (D) is a silicone rubber having a formula selected from (i)R¹R² ₂SiO(R² ₂SiO)_(a)SiR² ₂R¹ (IV) and (ii) R⁵R¹ ₂SiO(R¹R⁵SiO)_(b) SiR¹₂R⁵ (V); wherein R¹ is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀halogen-substituted hydrocarbyl, both free of aliphatic unsaturation, R²is R¹ or alkenyl, R⁵ is R¹ or —H, and subscripts a and b each have avalue of from 1 to 4, provided the silicone rubber (D)(i) has an averageof at least two silicon-bonded alkenyl groups per molecule, and thesilicone rubber (D)(ii) has an average of at least two silicon-bondedhydrogen atoms per molecule.

Component (D)(i) is at least one silicone rubber having the formula R¹R²₂SiO(R² ₂SiO)_(a)SiR² ₂R¹ (IV), wherein R¹ and R² are as described andexemplified above and the subscript a has a value of from 1 to 4,provided the silicone rubber (D)(i) has an average of at least twosilicon-bonded alkenyl groups per molecule. Alternatively, the subscripta has a value of from 2 to 4 or from 2 to 3.

Examples of silicone rubbers suitable for use as component (D)(i)include, but are not limited to, silicone rubbers having the followingformulae: ViMe₂SiO(Me₂SiO)_(a)SiMe2Vi, ViMe₂SiO(Ph₂SiO)_(a)SiMe₂Vi, andViMe₂SiO(PhMeSiO)_(a) SiMe₂Vi, where Me is methyl, Ph is phenyl, Vi isvinyl, and the subscript a has a value of from 1 to 4.

Component (D)(i) can be a single silicone rubber or a mixture comprisingtwo or more different silicone rubbers, each having the formula (IV).

Component (D)(ii) is at least one silicone rubber having the formulaR⁵R¹ ₂SiO (R¹R⁵SiO)_(b)SiR¹ ₂R⁵ (V); wherein R¹ and R⁵ are as describedand exemplified above, and the subscript b has a value of from 1 to 4,provided the silicone rubber (D)(ii) has an average of at least twosilicon-bonded hydrogen atoms per molecule. Alternatively, the subscriptb has a value of from 2 to 4 or from 2 to 3.

Examples of silicone rubbers suitable for use as component (D)(ii)include, but are not limited to, silicone rubbers having the followingformulae: HMe₂SiO(Me₂SiO)_(b)SiMe₂H, HMe₂SiO(Ph₂SiO)_(b)SiMe₂H,HMe₂SiO(PhMeSiO)_(b) SiMe₂H, and HMe₂SiO(Ph₂SiO)₂(Me₂SiO)₂SiMe₂H, whereMe is methyl, Ph is phenyl, and the subscript b has a value of from 1 to4.

Component (D)(ii) can be a single silicone rubber or a mixturecomprising two or more different silicone rubbers, each having theformula (V).

The mole ratio of silicon-bonded alkenyl groups or silicon-bondedhydrogen atoms in the silicone rubber (D) to silicon-bonded alkenylgroups in the silicone resin (A) is typically from 0.01 to 0.5,alternatively from 0.05 to 0.4, alternatively from 0.1 to 0.3.

Methods of preparing silicone rubbers containing silicon-bonded alkenylgroups or silicon-bonded hydrogen atoms are well known in the art; manyof these compounds are commercially available.

According to a fourth embodiment, the hydrosilylation-curable siliconecomposition comprises (A′) a silicone resin having the formula (R¹R⁵₂SiO_(1/2))_(w)(R⁵ ₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z)(III); (B′) an organosilicon compoundhaving an average of at least two silicon-bonded alkenyl groups permolecule in an amount sufficient to cure the silicone resin; (C) acatalytic amount of a photoactivated hydrosilylation catalyst; and (D) asilicone rubber having a formula selected from (i) R¹R² ₂SiO(R²₂SiO)_(a)SiR² ₂R¹ (IV) and (ii) R⁵R¹ ₂SiO(R¹R⁵SiO)_(b)SiR¹ ₂R⁵ (V);wherein R¹ is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, R² is R¹ or alkenyl,R⁵ is R¹ or —H, subscripts a an b each have a value of from 1 to 4, w isfrom 0 to 0.8, x is from 0 to 0.6, y is from 0 to 0.99, z is from 0 to0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) isfrom 0.01 to 0.8, provided the silicone resin and the silicone rubber(D)(ii) each have an average of at least two silicon-bonded hydrogenatoms per molecule, the silicone rubber (D)(i) has an average of atleast two silicon-bonded alkenyl groups per molecule, and the mole ratioof silicon-bonded alkenyl groups or silicon-bonded hydrogen atoms in thesilicone rubber (D) to silicon-bonded hydrogen atoms in the siliconeresin (A′) is from 0.01 to 0.5.

Components (A′), (B′), and (C) of the fourth embodiment of the siliconecomposition are as described and exemplified above for the secondembodiment, and component (D) of the fourth embodiment is as describedand exemplified above for the third embodiment.

The concentration of component (B′) is sufficient to cure (cross-link)the silicone resin of component (A′). When component (D) is (D)(i), theconcentration of component (B′) is such that the ratio of the sum of thenumber of moles of silicon-bonded alkenyl groups in component (B′) andcomponent (D)(i) to the number of moles of silicon-bonded hydrogen atomsin component (A′) is typically from 0.4 to 2, alternatively from 0.8 to1.5, alternatively from 0.9 to 1. 1. Furthermore, when component (D) is(D)(ii), the concentration of component (B′) is such that the ratio ofthe number of moles of silicon-bonded alkenyl groups in component (B′)to the sum of the number of moles of silicon-bonded hydrogen atoms incomponent (A′) and component (D)(ii) is typically from 0.4 to 2,alternatively from 0.8 to 1.5, alternatively from 0.9 to 1.1.

The mole ratio of silicon-bonded alkenyl groups or silicon-bondedhydrogen atoms in the silicone rubber (D) to silicon-bonded hydrogenatoms in the silicone resin (A′) is typically from 0.01 to 0.5,alternatively from 0.05 to 0.4, alternatively from 0.1 to 0.3.

According to a fifth embodiment, the hydrosilylation-curable siliconecomposition comprises (A″) a rubber-modified silicone resin prepared byreacting a silicone resin having the formula (R¹R² ₂SiO_(1/2))_(w)(R²₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z) (I) and a siliconerubber having the formula R⁵R¹ ₂SiO(R¹R⁵SiO)_(c)SiR¹ ₂R⁵ (VI) in thepresence of a hydrosilylation catalyst and, optionally, an organicsolvent to form a soluble reaction product, wherein R¹ is C₁ to C₁₀hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both free ofaliphatic unsaturation, R² is R¹ or alkenyl, R⁵ is R¹ or —H, c has avalue of from greater than 4 to 1,000, w is from 0 to 0.8, x is from 0to 0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1,y=z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided the silicone resin (I) has an average of at least twosilicon-bonded alkenyl groups per molecule, the silicone rubber (VI) hasan average of at least two silicon-bonded hydrogen atoms per molecule,and the mole ratio of silicon-bonded hydrogen atoms in the siliconerubber (VI) to silicon-bonded alkenyl groups in silicone resin (I) isfrom 0.01 to 0.5; (B) an organosilicon compound having an average of atleast two silicon-bonded hydrogen atoms per molecule in an amountsufficient to cure the rubber-modified silicone resin; and (C) acatalytic amount of a photoactivated hydrosilylation catalyst.

Components (B) and (C) of the fifth embodiment of the siliconecomposition are as described and exemplified above for the firstembodiment.

The concentration of component (B) is sufficient to cure (cross-link)the rubber-modified silicone resin. The concentration of component (B)is such that the ratio of the sum of the number of moles ofsilicon-bonded hydrogen atoms in component (B) and the silicone rubber(VI) to the number of moles of silicon-bonded alkenyl groups in thesilicone resin (I) is typically from 0.4 to 2, alternatively from 0.8 to1.5, alternatively from 0.9 to 1.1.

Component (A″) is a rubber-modified silicone resin prepared by reactingat least one silicone resin having the formula (R¹ R² ₂SiO_(1/2))_(w)(R²₂SiO_(2/2))_(x)(R¹ SiO_(3/2))_(y)(SiO_(4/2))_(z) (I) and at least onesilicone rubber having the formula R⁵R¹ ₂SiO(R¹R⁵SiO)_(c)SiR¹ ₂R⁵ (VI)in the presence of a hydrosilylation catalyst and, optionally, anorganic solvent to form a soluble reaction product, wherein R¹, R², R⁵,w, x, y, z, y+z/(w+x+y+z), and w+x/(w+x+y+z) are as described andexemplified above, and the subscript c has a value of from greater than4 to 1,000.

The silicone resin having the formula (I) is as described andexemplified above for the first embodiment of the silicone composition.Also, the hydrosilylation catalyst and organic solvent are as describedand exemplified above in the method of preparing theorganohydrogenpolysiloxane resin having the formula (II). As used hereinthe term “soluble reaction product” means when organic solvent ispresent, the product of the reaction for preparing component (A″) ismiscible in the organic solvent and does not form a precipitate orsuspension.

In the formula (VI) of the silicone rubber, R¹ and R⁵ are as describedand exemplified above, and the subscript c typically has a value of fromgreater than 4 to 1,000, alternatively from 10 to 500, alternativelyfrom 10 to 50.

Examples of silicone rubbers having the formula (VI) include, but arenot limited to, silicone rubbers having the following formulae:HMe₂SiO(Me₂SiO)₅₀SiMe₂H, HMe₂SiO(Me₂SiO)₁₀SiMe₂H, HMe₂SiO(PhMeSiO)₂₅SiMe₂H, and Me₃SiO(MeHSiO)₁₀SiMe₃, wherein Me is methyl, Ph is phenyl,and the numerical subscripts indicate the number of each type ofsiloxane unit.

The silicone rubber having the formula (VI) can be a single siliconerubber or a mixture comprising two or more different silicone rubbers,each having the formula (VI).

Methods of preparing silicone rubbers containing silicon-bonded hydrogenatoms are well known in the art; many of these compounds arecommercially available.

The silicone resin (I), silicone rubber (VI), hydrosilylation catalyst,and organic solvent can be combined in any order. Typically, thesilicone resin, silicone rubber, and organic solvent are combined beforethe introduction of the hydrosilylation catalyst.

The reaction is typically carried out at a temperature of from roomtemperature (˜23±2° C.) to 150° C., alternatively from room temperatureto 100° C.

The reaction time depends on several factors, including the structuresof the silicone resin and the silicone rubber, and the temperature. Thecomponents are typically allowed to react for a period of timesufficient to complete the hydrosilylation reaction. This means thecomponents are typically allowed to react until at least 95 mol %,alternatively at least 98 mol %, alternatively at least 99 mol %, of thesilicon-bonded hydrogen atoms originally present in the silicone rubberhave been consumed in the hydrosilylation reaction, as determined byFTIR spectrometry. The time of reaction is typically from 0.5 to 24 h ata temperature of from room temperature (˜23±2° C.) to 100° C. Theoptimum reaction time can be determined by routine experimentation usingthe methods set forth in the Examples section below.

The mole ratio of silicon-bonded hydrogen atoms in the silicone rubber(VI) to silicon-bonded alkenyl groups in the silicone resin (I) istypically from 0.01 to 0.5, alternatively from 0.05 to 0.4,alternatively from 0.1 to 0.3.

The concentration of the hydrosilylation catalyst is sufficient tocatalyze the addition reaction of the silicone resin (I) with thesilicone rubber (VI). Typically, the concentration of thehydrosilylation catalyst is sufficient to provide from 0.1 to 1000 ppmof a platinum group metal, based on the combined weight of the resin andthe rubber.

The concentration of the organic solvent is typically from 0 to 95%(w/w), alternatively from 10 to 75% (w/w), alternatively from 40 to 60%(w/w), based on the total weight of the reaction mixture.

The rubber-modified silicone resin can be used without isolation orpurification in the fifth embodiment of the hydrosilylation-curablesilicone composition or the resin can be separated from most of thesolvent by conventional methods of evaporation. For example, thereaction mixture can be heated under reduced pressure. Moreover, whenthe hydrosilylation catalyst is a supported catalyst, described above,the rubber-modified silicone resin can be readily separated from thehydrosilylation catalyst by filtering the reaction mixture. However,when the rubber-modified silicone resin is not separated from thehydrosilylation catalyst used to prepare the resin, the catalyst may beused as component (C) of the fifth embodiment of thehydrosilylation-curable silicone composition.

According to a sixth embodiment, the hydrosilylation-curable siliconecomposition comprises (A′″) a rubber-modified silicone resin prepared byreacting a silicone resin having the formula (R¹ ⁵ ₂SiO_(1/2))_(w)(R⁵₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z)(III) and a siliconerubber having the formula R¹ ² ₂SiO(R² ₂SiO)_(d)SiR² ₂R¹ (VII) in thepresence of a hydrosilylation catalyst and, optionally, an organicsolvent to form a soluble reaction product, wherein R¹ is C₁ to C₁₀hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both free ofaliphatic unsaturation, R² is R¹ or alkenyl, R⁵ is R¹ or —H, subscript dhas a value of from greater than 4 to 1,000,w is from 0 to 0.8,x is from0 to 0.6,y is from 0 to 0.99,z is from 0 to 0.35, w+x+y+z=1,y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided the silicone resin (III) has an average of at least twosilicon-bonded hydrogen atoms per molecule, the silicone rubber (VII)has an average of at least two silicon-bonded alkenyl groups permolecule, and the mole ratio of silicon-bonded alkenyl groups in thesilicone rubber (VII) to silicon-bonded hydrogen atoms in the siliconeresin (III) is from 0.01 to 0.5; (B′) an organosilicon compound havingan average of at least two silicon-bonded alkenyl groups per molecule inan amount sufficient to cure the rubber-modified silicone resin; and (C)a catalytic amount of a photoactivated hydrosilylation catalyst.

Components (B′) and (C) of the sixth embodiment of the siliconecomposition are as described and exemplified above for the secondembodiment.

The concentration of component (B′) is sufficient to cure (cross-link)the rubber-modified silicone resin. The concentration of component (B′)is such that the ratio of the sum of the number of moles ofsilicon-bonded alkenyl groups in component (B′) and the silicone rubber(VII) to the number of moles of silicon-bonded hydrogen atoms in thesilicone resin (III) is typically from 0.4 to 2, alternatively from 0.8to 1.5, alternatively from 0.9 to 1.1.

Component (A′″) is a rubber-modified silicone resin prepared by reactingat least one silicone resin having the formula (R¹R⁵ ₂SiO_(1/2))_(w)(R⁵₂SiO_(2/2))_(x()R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z) (III) and at least onesilicone rubber having the formula R¹R² ₂SiO(R² ₂SiO)_(d)SiR² ₂R¹ (VII)in the presence of a hydrosilylation catalyst and an organic solvent toform a soluble reaction product, wherein R¹, R², R⁵, w, x, y, z,y+z/(w+x+y+z), and w+x/(w+x+y+z) are as described and exemplified above,and the subscript d has a value of from greater than 4 to 1,000.

The silicone resin having the formula (III) is as described andexemplified above for the second embodiment of thehydrosilylation-curable silicone composition. Also, the hydrosilylationcatalyst and organic solvent are as described and exemplified above inthe method of preparing the organohydrogenpolysiloxane resin having theformula (II). As in the previous embodiment of the silicone composition,the term “soluble reaction product” means when organic solvent ispresent, the product of the reaction for preparing component (A′″) ismiscible in the organic solvent and does not form a precipitate orsuspension.

In the formula (VII) of the silicone rubber, R¹ and R² are as describedand exemplified above, and the subscript d typically has a value of from4 to 1,000, alternatively from 10 to 500, alternatively form 10 to 50.

Examples of silicone rubbers having the formula (VII) include, but arenot limited to silicone rubbers having the following formulae:ViMe₂SiO(Me₂SiO)₅₀SiMe₂Vi, ViMe₂SiO(Me₂SiO)₁₀SiMe₂Vi,ViMe₂SiO(PhMeSiO)₂₅ SiMe₂Vi, and Vi₂MeSiO(PhMeSiO)₂₅SiMe₂Vi, wherein Meis methyl, Ph is phenyl, Vi is vinyl, and the numerical subscriptsindicate the number or each type of siloxane unit.

The silicone rubber having the formula (VII) can be a single siliconerubber or a mixture comprising two or more different silicone rubbers,each having the formula (VII).

Methods of preparing silicone rubbers containing silicon-bonded alkenylgroups are well known in the art; many of these compounds arecommercially available.

The reaction for preparing component (A′″) can be carried out in themanner described above for preparing component (A″) of the fifthembodiment of the silicone composition, except the silicone resin havingthe formula (I) and the silicone rubber having the formula (VI) arereplaced with the resin having the formula (III) and the rubber havingthe formula (VII), respectively. The mole ratio of silicon-bondedalkenyl groups in the silicone rubber (VII) to silicon-bonded hydrogenatoms in the silicone resin (III) is from 0.01 to 0.5, alternativelyfrom 0.05 to 0.4, alternatively from 0.1 to 0.3. Moreover, the siliconeresin and the silicone rubber are typically allowed to react for aperiod of time sufficient to complete the hydrosilylation reaction. Thismeans the components are typically allowed to react until at least 95mol %, alternatively at least 98 mol %, alternatively at least 99 mol %,of the silicon-bonded alkenyl groups originally present in the rubberhave been consumned in the hydrosilylation reaction, as determined byFTIR spectrometry.

The hydrosilylation-curable silicone composition of the present methodcan comprise additional ingredients, provided the ingredient does notprevent the silicone composition from curing to form a cured siliconeresin having low coefficient of thermal expansion, high tensilestrength, and high modulus, as described below. Examples of additionalingredients include, but are not limited to, hydrosilylation catalystinhibitors, such as 3-methyl-3-penten-1-yne, 3,5-dimethyl-3-hexen-1-yne,3,5-dimethyl-1-hexyn-3-ol, 1-ethynyl-1-cyclohexanol,2-phenyl-3-butyn-2-ol, vinylcyclosiloxanes, and triphenylphosphine;adhesion promoters, such as the adhesion promoters taught in U.S. Pat.Nos. 4,087,585 and 5,194,649; dyes; pigments; anti-oxidants; heatstabilizers; UV stabilizers; flame retardants; flow control additives;and diluents, such as organic solvents and reactive diluents.

For example, the hydrosilylation-curable silicone composition cancontain (E) a reactive diluent comprising (i) an organosiloxane havingan average of at least two silicon-bonded alkenyl groups per moleculeand a viscosity of from 0.001 to 2 Pa·s at 25° C., wherein the viscosityof (E)(i) is not greater than 20% of the viscosity of the siliconeresin, e.g., component (A), (A′), (A″), or (A′″) above, of the siliconecomposition and the organosiloxane has the formula (R¹R²₂SiO_(1/2))_(m)(R² ₂SiO_(2/2))_(n)(R¹SiO_(3/2))_(p)(SiO_(4/2))_(q,)wherein R¹is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, R² is R¹ or alkenyl, mis 0 to 0.8, n =0 to 1, p=0 to 0.25, q=0 to 0.2, m+n+p+q=1, and m+n isnot equal to 0, provided when p+q=0, n is not equal to 0 and the alkenylgroups are not all terminal, and (ii) an organohydrogensiloxane havingan average of at least two silicon-bonded hydrogen atoms per moleculeand a viscosity of from 0.001 to 2 Pa·s at 25° C., in an amountsufficient to provide from 0.5 to 3 moles of silicon-bonded hydrogenatoms in (E)(ii) per mole of alkenyl groups in (E)(i), wherein theorganohydrogensiloxane has the formula (HR¹₂SiO_(1/2))_(s)(R¹SiO_(3/2))_(t)(SiO_(4/2))_(v), wherein R¹is C₁ to C₁₀hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both free ofaliphatic unsaturation, s is from 0.25 to 0.8, t is from 0 to 0.5, v isfrom 0 to 0.3, s+t+v=1, and t+v is not equal to 0.

Component (E)(i) is at least one organosiloxane having an average of atleast two alkenyl groups per molecule and a viscosity of from 0.001 to 2Pa·s at 25° C., wherein the viscosity of (E)(i) is not greater than 20%of the viscosity of the silicone resin of the silicone composition andthe organosiloxane has the formula (R¹R² ₂SiO_(1/2))_(m) (R²₂SiO_(2/2))_(n)(R¹SiO_(3/2))_(p)(SiO_(4/2))_(q,) wherein R¹is C₁ to C₁₀hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both free ofaliphatic unsaturation, R² is R¹ or alkenyl, m is 0 to 0.8, n=0 to 1,p=0 to 0.25, q=0 to 0.2, m+n+p+q=1, and m+n is not equal to 0, providedwhen p+q=0, n is not equal to 0 and the alkenyl groups are not allterminal (i.e., not all the alkenyl groups in the organosiloxane are inthe R¹R² ₂SiO_(1/2) units). Further, organosiloxane (E)(i) can have alinear, branched, or cyclic structure. For example, when the subsciptsm, p, and q in the formula of organosiloxane (E)(i) are each equal to 0,the organosiloxane is an organocyclosiloxane.

The viscosity of organosiloxane (E)(i) at 25° C. is typically from 0.001to 2 Pa·s, alternatively from 0.001 to 0.1 Pa·s, alternatively from0.001 to 0.05 Pa·s. Further, the viscosity of organosiloxane (E)(i) at25° C. is typically not greater than 20%, alternatively not greater than10%, alternatively not greater than 1%, of the viscosity of the siliconeresin in the hydrosilylation-curable silicone composition.

Examples of organosiloxanes suitable for use as organosiloxane (E)(i)include, but are not limited to, organosiloxanes having the followingformulae: (ViMeSiO)₃, (ViMeSiO)₄, (ViMeSiO)₅, (ViMeSiO)₆, (ViPhSiO)₃,(ViPhSiO)₄, (ViPhSiO)₅, (ViPhSiO)₆, ViMe₂SiO(ViMeSiO)_(n)SiMe₂Vi,Me₃SiO(ViMeSiO)_(n)SiMe₃, and (ViMe₂SiO)₄Si, where Me is methyl, Ph isphenyl, Vi is vinyl, and the subscript n has a value such that theorganosiloxane has a viscosity of from 0.001 to 2 Pa·s at 25° C.

Component (E)(i) can be a single organosiloxane or a mixture comprisingtwo or more different organosiloxanes, each as described above. Methodsof making alkenyl-functional organosiloxanes are well known in the art.

Component (E)(ii) is at least one organohydrogensiloxane having anaverage of at least two silicon-bonded hydrogen atoms per molecule and aviscosity of from 0.001 to 2 Pa·s at 25° C., in an amount sufficient toprovide from 0.5 to 3 moles of silicon-bonded hydrogen atoms in (E)(ii)to moles of alkenyl groups in (E)(i), wherein the organohydrogensiloxanehas the formula (HR¹ ₂SiO_(1/2))s(R¹SiO_(3/2))_(t)(SiO_(4/2))_(v,)wherein R¹is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substitutedhydrocarbyl, both free of aliphatic unsaturation, s is from 0.25 to 0.8,t is from 0 to 0.5, v is from 0 to 0.3, s+t+v=1, and t+v is not equal to0.

The viscosity of organohydrogensiloxane (E)(ii) at 25° C. is typicallyfrom 0.001 to 2 Pa·s, alternatively from 0.001 to 0.1 Pa·s,alternatively from 0.001 to 0.05 Pa·s.

Examples of organohydrogensiloxanes suitable for use asorganohydrogensiloxane (E)(ii) include, but are not limited to,organohydrogensiloxanes having the following formulae: PhSi(OSiMe₂H)₃,Si(OSiMe₂H)₄, MeSi(OSiMe₂H)₃, (HMe₂SiO)₃SiOSi(OSiMe₂H)₃, and(HMe₂SiO)₃SiOSi(Ph)(OSiMe₂H)₂, where Me is methyl and Ph is phenyl.

Component (E)(ii) can be a single organohydrogensiloxane or a mixturecomprising two or more different organohydrogensiloxanes, each asdescribed above. Methods of making organohydrogensiloxanes are wellknown in the art.

The concentration of component (E)(ii) is sufficient to provide from 0.5to 3 moles of silicon-bonded hydrogen atoms, alternatively from 0.6 to 2moles of silicon-bonded hydrogen atoms, alternatively from 0.9 to 1.5moles of silicon-bonded hydrogen atoms, per mole of alkenyl groups incomponent (E)(i).

The concentration of the reactive diluent (E), component (E)(i) and(E)(ii) combined, in the hydrosilylation-curable silicone composition istypically from 0 to 90% (w/w), alternatively from 0 to 50% (w/w),alternatively from 0 to 20% (w/w), alternatively from 0 to 10% (w/w),based on the combined weight of the silicone resin, component (A),(A′),(A″), or (A′″), and the organosilicon compound, component (B) or(B′) in the embodiments above.

The silicone composition can be a one-part composition comprising thesilicone resin, organosilicon compound, and photoactivatedhydrosilylation catalyst in a single part or, alternatively, amulti-part composition comprising these components in two or more parts.For example, a multi-part silicone composition can comprise a first partcontaining a portion of the silicone resin and all of the photoactivatedhydrosilylation catalyst, and a second part containing the remainingportion of the silicone resin and all of the organosilicon compound.

The one-part silicone composition is typically prepared by combining theprincipal components and any optional ingredients in the statedproportions at ambient temperature, with or without the aid of anorganic solvent. Although the order of addition of the variouscomponents is not critical if the silicone composition is to be usedimmediately, the hydrosilylation catalyst is preferably added last at atemperature below about 30° C. to prevent premature curing of thecomposition. Also, the multi-part silicone composition can be preparedby combining the components in each part.

Mixing can be accomplished by any of the techniques known in the artsuch as milling, blending, and stirring, either in a batch or continuousprocess. The particular device is determined by the viscosity of thecomponents and the viscosity of the final silicone composition.

The fiber reinforcement can be any reinforcement comprising fibers,provided the reinforcement has a high modulus and high tensile strength.The fiber reinforcement typically has a Young's modulus at 25° C. of atleast 3 GPa. For example, the reinforcement typically has a Young'smodulus at 25° C. of from 3 to 1,000 GPa, alternatively from 3 to 200GPa, alternatively from 10 to 100 GPa. Moreover, the reinforcementtypically has a tensile strength at 25° C. of at least 50 MPa. Forexample, the reinforcement typically has a tensile strength at 25° C. offrom 50 to 10,000 MPa, alternatively from 50 to 1,000 MPa, alternativelyfrom 50 to 500 MPa.

The fiber reinforcement can be a woven fabric, e.g., a cloth; a nonwovenfabric, e.g., a mat or roving; or loose (individual) fibers. The fibersin the reinforcement are typically cylindrical in shape and have adiameter of from 1 to 100 μm, alternatively from 1 to 20 μm,alternatively form 1 to 10 μm. Loose fibers may be continuous, meaningthe fibers extend throughout the reinforced silicone resin film in agenerally unbroken manner, or chopped.

The fiber reinforcement is typically heat-treated prior to use to removeorganic contaminants. For example, the fiber reinforcement is typicallyheated in air at an elevated temperature, for example, 575° C., for asuitable period of time, for example 2 h.

Examples of fiber reinforcements include, but are not limited toreinforcements comprising glass fibers; quartz fibers; graphite fibers;nylon fibers; polyester fibers; aramid fibers, such as Kevlar® andNomex®; polyethylene fibers; polypropylene fibers; and silicon carbidefibers.

The fiber reinforcement can be impregnated in a hydrosilylation-curablesilicone composition using a variety of methods. For example, accordingto a first method, the fiber reinforcement can be impregnated by (i)applying a hydrosilylation-curable silicone composition to a releaseliner to form a silicone film; (ii) embedding a fiber reinforcement inthe film; (iii) degassing the embedded fiber reinforcement; and (iv)applying the silicone composition to the degassed embedded fiberreinforcement to form an impregnated fiber reinforcement.

In step (i), a hydrosilylation-curable silicone composition, describedabove, is applied to a release liner to form a silicone film. Therelease liner can be any rigid or flexible material having a surfacefrom which the reinforced silicone resin film can be removed withoutdamage by delamination after the silicone resin is cured, as describedbelow. Examples of release liners include, but are not limited to,Nylon, polyethyleneterephthalate, and polyimide.

The silicone composition can be applied to the release liner usingconventional coating techniques, such as spin coating, dipping,spraying, brushing, or screen-printing. The silicone composition isapplied in an amount sufficient to embed the fiber reinforcement in step(ii), below.

In step (ii), a fiber reinforcement is embedded in the silicone film.The fiber reinforcement can be embedded in the silicone film by simplyplacing the reinforcement on the film and allowing the siliconecomposition of the film to saturate the reinforcement.

In step (iii), the embedded fiber reinforcement is degassed. Theembedded fiber reinforcement can be degassed by subjecting it to avacuum at a temperature of from room temperature (˜23±2° C.) to 60° C.,for a period of time sufficient to remove entrapped air in the embeddedreinforcement. For example, the embedded fiber reinforcement cantypically be degassed by subjecting it to a pressure of from 1,000 to20,000 Pa for 5 to 60 min. at room temperature.

In step (iv), the silicone composition is applied to the degassedembedded fiber reinforcement to form an impregnated fiber reinforcement.The silicone composition can be applied to the degassed embedded fiberreinforcement using conventional methods, as described above for step(i).

The first method can further comprise the step of (v) degassing theimpregnated fiber reinforcement.

Alternatively, according to a second method, the fiber reinforcement canbe impregnated in a hydrosilylation-curable silicone composition by (i)depositing a fiber reinforcement on a release liner; (ii) embedding thefiber reinforcement in a hydrosilylation-curable silicone composition;(iii) degassing the embedded fiber reinforcement; and (iv) applying thesilicone composition to the degassed embedded fiber reinforcement toform an impregnated fiber reinforcement. The second method can furthercomprise the step of (v) degassing the impregnated fiber reinforcement.In the second method, steps (iii) to (v) are as described above for thefirst method of impregnating a fiber reinforcement in ahydrosilylation-curable silicone composition.

In step (ii), the fiber reinforcement is embedded in ahydrosilylation-curable silicone composition. The reinforcement can beembedded in the silicone composition by simply covering thereinforcement with the composition and allowing the composition tosaturate the reinforcement.

Furthermore, when the fiber reinforcement is a woven or nonwoven fabric,the reinforcement can be impregnated in a hydrosilylation-curablesilicone composition by passing it through the composition. The fabricis typically passed through the silicone composition at a rate of from 1to 1,000 cm/s at room temperature (˜23±2° C.).

In the second step of the method of preparing a reinforced siliconeresin film, the impregnated fiber reinforcement is exposed to radiationtypically having a wavelength of from 150 to 800 nm, alternatively from250 to 400 nm, at a dosage sufficient to cure (cross-link) the siliconeresin. The light source is typically a medium pressure mercury-arc lamp.The dose of radiation is typically from 10 to 20,000 mJ/cm²,alternatively from 100 to 2,000 mJ/cm².

The reinforced silicone resin film of the present invention typicallycomprises from 10 to 99% (w/w), alternatively from 30 to 95% (w/w),alternatively from 60 to 95% (w/w), alternatively from 80 to 95% (w/w),of the cured silicone resin. Also, the reinforced silicone resin filmtypically has a thickness of from 15 to 500 μm, alternatively from 15 to300 μm, alternatively from 20 to 150 μm, alternatively from 30 to 125μm.

The reinforced silicone resin film typically has a flexibility such thatthe film can be bent over a cylindrical steel mandrel having a diameterless than or equal to 3.2 mm without cracking, where the flexibility isdetermined as described in ASTM Standard D522-93a, Method B.

The reinforced silicone resin film has low coefficient of linear thermalexpansion (CTE), high tensile strength, and high modulus. For examplethe film typically has a CTE of from 0 to 80 μm/m° C., alternativelyfrom 0 to 20 μm/m° C., alternatively from 2 to 10 μm/m° C., attemperature of from room temperature (˜23±2° C.) to 200° C. Also, thefilm typically has a tensile strength at 25° C. of from 50 to 200 MPa,alternatively from 80 to 200 MPa, alternatively from 100 to 200 MPa.Further, the reinforced silicone resin film typically has a Young'smodulus at 25° C. of from 2 to 10 GPa, alternatively from 2 to 6 GPa,alternatively from 3 to 5 GPa.

The transparency of the reinforced silicone resin film depends on anumber of factors, such as the composition of the cured silicone resin,the thickness of the film, and the refractive index of the fiberreinforcement. The reinforced silicone resin film typically has atransparency (% transmittance) of at least 50%, alternatively at least60%, alternatively at least 75%, alternatively at least 85%, in thevisible region of the electromagnetic spectrum.

The method of the present invention can further comprise forming acoating on at least a portion of the reinforced silicone resin film.Examples of coatings include, but are not limited to, cured siliconeresins prepared by curing hydrosilylation-curable silicone resins orcondensation-curable silicone resins; cured silicone resins prepared bycuring sols of organosilsesquioxane resins; inorganic oxides, such asindium tin oxide, silicon dioxide, and titanium dioxide; inorganicnitrides, such as silicon nitride and gallium nitride; metals, such ascopper, silver, gold, nickel, and chromium; and silicon, such asamorphous silicon, microcrystalline silicon, and polycrystallinesilicon.

The reinforced silicone resin film of the present invention has lowcoefficient of thermal expansion, high tensile strength, and highmodulus compared to an un-reinforced silicone resin film prepared fromthe same silicone composition. Also, although the reinforced andun-reinforced silicone resin films have comparable glass transitiontemperatures, the reinforced film exhibits a much smaller change inmodulus in the temperature range corresponding to the glass transition.

The reinforced silicone resin film of the present invention is useful inapplications requiring films having high thermal stability, flexibility,mechanical strength, and transparency. For example, the silicone resinfilm can be used as an integral component of flexible displays, solarcells, flexible electronic boards, touch screens, fire-resistantwallpaper, and impact-resistant windows. The film is also a suitablesubstrate for transparent or nontransparent electrodes.

EXAMPLES

The following examples are presented to better illustrate the method andreinforced silicone resin film of the present invention, but are not tobe considered as limiting the invention, which is delineated in theappended claims. Unless otherwise noted, all parts and percentagesreported in the examples are by weight. The following methods andmaterials were employed in the examples:

Measurement of Mechanical Properties

Young's modulus, tensile strength, and tensile strain at break weremeasured using an MTS Alliance RT/5 testing frame, equipped with a 100-Nload cell. Young's modulus, tensile strength, and tensile strain weredetermined at room temperature (˜23±2° C.) for the test specimens ofExamples 4 and 5. Young's modulus was measured at −100° C., 25° C., 100° C., 200° C., 300° C., and 400° C., for the test specimens of Examples6 and 7.

The test specimen was loaded into two pneumatic grips spaced apart 25 mmand pulled at a crosshead speed of 1 mm/min. Load and displacement datawere continuously collected. The steepest slope in the initial sectionof the load-displacement curve was taken as the Young's modulus.Reported values for Young's modulus (GPa), tensile strength (MPa), andtensile strain (%) each represent the average of three measurements madeon different dumbbell-shaped test specimens from the same reinforcedsilicone resin film.

The highest point on the load-displacement curve was used to calculatethe tensile strength according to the equation:

σ=F/(wb),

where:

σ=tensile strength, MPa,

F=highest force, N,

w=width of the test specimen, mm, and

b=thickness of the test specimen, mm.

The tensile strain at break was approximated by dividing the differencein grip separation before and after testing by the initial separationaccording to the equation:

ε=100(l ₂ −l ₁)/l ₁,

where:

ε=tensile strain at break, %,

l₂=final separation of the grips, mm, and

l₁=initial separation of the grips, mm.

Impregnated fiber reinforcements were irradiated using a Colite UVSystem (Colite International, Ltd.) equipped with a 300-W bulb.

WN1500 Vacuum Bagging Film, sold by Airtech, Inc. (Huntington Beach,Calif.), is a nylon bagging film having a thickness of 50 mm.

Glass Fabric, which is available from JPS Glass (Slater, S.C.), is anuntreated style 106 electrical glass fabric having a plain weave and athickness of 37.5 μm.

Example 1

This example demonstrates the preparation of the silicone resin used inExamples 3-5. Trimethoxyphenylsilane (200 g),tetramethyldivinyldisiloxane (38.7 g), deionized water (65.5 g), toluene(256 g), and trifluoromethanesulfonic acid (1.7 g) were combined in a3-neck, round-bottom flask equipped with a Dean-Stark Trap andthermometer. The mixture was heated at 60 to 65° C. for 2 hours. Themixture was then heated to reflux and water and methanol were removedusing a Dean-Stark trap. When the temperature of the mixture reached 80°C. and the removal of water and methanol was complete, the mixture wascooled to less than 50° C. Calcium carbonate (3.3 g) and water (about 1g) were added to the mixture. The mixture was stirred at roomtemperature for 2 hours and then potassium hydroxide (0.17 g) was addedto the mixture. The mixture was then heated to reflux and water wasremoved using a Dean-Stark trap. When the reaction temperature reached120° C. and the removal of water was complete, the mixture was cooled toless than 40° C. Chlorodimethylvinylsilane (0.37 g) was added to themixture and mixing was continued at room temperature for 1 hour. Themixture was filtered to give a solution of a silicone resin having theformula (PhSiO_(3/2))_(0.75)(ViMe₂SiO_(1/2))_(0.25) in toluene. Theresin has a weight-average molecular weight of about 1700, has anumber-average molecular weight of about 1440, and contains about 1 mol% of silicon-bonded hydroxy groups.

The volume of the solution was adjusted to produce a solution containing79.5 percent by weight of the silicone resin in toluene. The resinconcentration of a solution was determined by measuring the weight lossafter drying a sample (2.0 g) of the solution in an oven at 150° C. for1.5 hours.

Example 2

This example describes the preparation of 1,4-bis(dimethylsilyl)benzene.Magnesium (84 g) and tetrahydrofuran (406 g) were combined undernitrogen in a 5-L, three-neck flask equipped with a mechanical stirrer,condenser, two addition funnels, and thermometer. 1,2-dibromoethane (10g) was added to the mixture and the contents of the flask were heated to50 to 60° C. Tetrahydrofuran (THF, 200 mL) and a solution of1,2-dibromobenzene (270 g) in THF (526 g) were sequentially added to themixture, the latter in a drop-wise manner. After about twenty minutes,heating was discontinued and the remainder of the 1,2-dibromobenzene wasadded over a period of about 1.5 hours at such a rate as to maintain agentle reflux. During the addition, THF was periodically added tomaintain a reaction temperature less than about 65° C. After theaddition of the 1,2-dibromobenzene was complete, THF (500 mL) was addedto the flask and the mixture was heated at 65° C. for 5 hours. Heatingwas discontinued and the reaction mixture was stirred at roomtemperature overnight under nitrogen.

THF (500 mL) was added to the mixture and the flask was placed in an icewater bath. A dry-ice condenser was inserted into the top of the watercondenser and chlorodimethylsilane (440 g) was added drop-wise to themixture at such a rate as to maintain reflux. After the addition wascomplete, the flask was removed from the ice water bath and the mixturewas heated at 60° C. overnight. The mixture was cooled to roomtemperature and treated sequentially with toluene (1000 mL) andsaturated aqueous NH₄Cl (1500 mL). The contents of the flask weretransferred to a separatory funnel and washed with several portions ofwater until a substantially transparent organic layer was obtained. Theorganic layer was removed, dried over magnesium sulfate, andconcentrated by distillation until the temperature of the residuereached 150° C. The concentrated crude product was purified by vacuumdistillation. A fraction was collected at 125-159° C. under a pressureof 12 mmHg (1600 Pa) to give p-bis(dimethylsilyl) benzene (140 g) as acolorless liquid. The identity of the product was confirmed by GC-MS,FT-IR, ¹H NMR, and ¹³C NMR.

Example 3

The resin solution of Example 1 was mixed with1,4-bis(dimethylsilyl)benzene, the relative amounts of the twoingredients sufficient to achieve a mole ratio of silicon-bondedhydrogen atoms to silicon-bonded vinyl groups (SiH/SiVi) of 1.1:1, asdetermined by ²⁹Si NMR and ¹³C NMR. The mixture was heated at 80° C.under a pressure of 5 mmHg (667 Pa) to remove the toluene. Then, a smallamount of 1,4-bis(dimethylsilyl) benzene was added to the mixture torestore the mole ratio SiH/SiVi to 1.1:1. To the mixture was added 4%(w/w), based on the combined weight of the resin and1,4-bis(dimethylsilyl)benzene, of a photoactivated hydrosilylationcatalyst containing 1.6 g of platinum(II) acetylacetonate and 158.4 g ofethyl lactate.

Example 4

A flat glass plate (25.4 cm×38.1 cm) was covered with a Nylon film(WN1500 Vacuum Bagging Film) to form a release liner. The siliconecomposition of Example 3 was uniformly applied to the Nylon film using aNo. 16 Mylar® metering rod to form a silicone film. Glass fabric havingthe same dimensions as the Nylon film was carefully laid down on thesilicone film, allowing sufficient time for the composition tothoroughly wet the fabric. The embedded fabric was then degassed undervacuum (5.3 kPa) at room temperature for 0.5 h. The silicone compositionof Example 3 was then uniformly applied to the degassed embedded fabricand the degassing procedure was repeated. The impregnated glass fabricwas exposed to radiation having a wavelength of 365 nm at a dosage ofapproximately 12000 mJ/m². The glass fiber-reinforced silicone resinfilm was separated from the Nylon film. The reinforced film had auniform thickness (0.100-0.115 mm) and was substantially transparent andfree of voids. One surface of the reinforced film was embossed with thesurface texture of the release liner (Nylon film). The mechanicalproperties of the glass fiber-reinforced silicone resin film are shownin Table 1.

Example 5

A glass fiber-reinforced silicone resin film was prepared according tothe method of Example 4, except the silicone composition contained 2%(w/w), based on the combined weight of the resin and1,4-bis(dimethylsilyl)benzene, of the photoactivated hydrosilylationcatalyst. The mechanical properties of the glass fiber-reinforcedsilicone resin film are shown in Table 1.

TABLE 1 Tensile Strength (MPa) Young's Modulus (GPa) Strain at Break (%)Ex. Thickness (mm) Warp Fill Warp Fill Warp Fill 4 0.100-0.110 68.7 ±5.7 58.3 ± 3.4 2.80 ± 0.43 2.77 ± 0.04 3.8 ± 1.1 2.9 ± 0.5 5 0.110-0.11543.7 ± 4.3 65.9 ± 1.8 1.63 ± 0.10 2.29 ± 0.34 3.3 ± 0.5 4.1 ± 0.5

1. A method of preparing a reinforced silicone resin film, the methodcomprising the steps of: impregnating a fiber reinforcement in ahydrosilylation-curable silicone composition comprising a silicone resinand a photoactivated hydrosilylation catlayst; and exposing theimpregnated fiber reinforcement to radiation having a wavelength of from150 to 800 nm at a dosage sufficient to cure the silicone resin; whereinthe reinforced silicone resin film comprises from 10 to 99% (w/w) of thecured silicone resin and the film has a thickness of from 15 to 500 μm.2. The method according to claim 1, wherein the hydrosilylation-curablesilicone composition comprises (A) a silicone resin having the formula(R¹R² ₂SiO_(1/2))_(w) (R²₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z) (I), wherein R¹is C₁ toC₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both freeof aliphatic unsaturation, R² is R¹ or alkenyl, w is from 0 to 0.8, x isfrom 0 to 0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1,y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided the silicone resin has an average of at least twosilicon-bonded alkenyl groups per molecule; (B) an organosiliconcompound having an average of at least two silicon-bonded hydrogen atomsper molecule in an amount sufficient to cure the silicone resin; and (C)a catalytic amount of a photoactivated hydrosilylation catalyst.
 3. Themethod according to claim 1, wherein the hydrosilylation-curablesilicone composition comprises (A′) a silicone resin having the formula(R¹R⁵ ₂SiO_(1/2))_(w) (R⁵₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z) (III), wherein R¹is C₁to C₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, bothfree of aliphatic unsaturation, R⁵ is R¹ or —H, w is from 0 to 0.8, x isfrom 0 to 0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1,y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided the silicone resin has an average of at least twosilicon-bonded hydrogen atoms per molecule; (B′) an organosiliconcompound having an average of at least two silicon-bonded alkenyl groupsper molecule in an amount sufficient to cure the silicone resin; and (C)a catalytic amount of a photoactivated hydrosilylation catalyst.
 4. Themethod according to claim 1, wherein the hydrosilylation-curablesilicone composition comprises (A) a silicone resin having the formula(R¹R² ₂SiO_(1/2))_(w) (R²₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z) (I); (B) anorganosilicon compound having an average of at least two silicon-bondedhydrogen atoms per molecule in an amount sufficient to cure the siliconeresin; (C) a catalytic amount of a photoactivated hydrosilylationcatalyst; and (D) a silicone rubber having a formula selected from (i)R¹R² ₂SiO(R² ₂SiO)_(a)SiR² ₂R¹ (IV) and (ii) R⁵R¹ ₂SiO(R¹R⁵SiO)_(b)SiR¹₂R⁵ (V); wherein R¹ is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀halogen-substituted hydrocarbyl, both free of aliphatic unsaturation, R²is R¹ or alkenyl, R⁵ is R¹ or —H, subscripts a and b each have a valueof from 1 to 4, w is from 0 to 0.8, x is from 0 to 0.6, y is from 0 to0.99, z is from 0 to 0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99,and w+x/(w+x+y+z) is from 0.01 to 0.8, provided the silicone resin andthe silicone rubber (D)(i) each have an average of at least twosilicon-bonded alkenyl groups per molecule, the silicone rubber (D)(ii)has an average of at least two silicon-bonded hydrogen atoms permolecule, and the mole ratio of silicon-bonded alkenyl groups orsilicon-bonded hydrogen atoms in the silicone rubber (D) tosilicon-bonded alkenyl groups in the silicone resin (A) is from 0.01 to0.5.
 5. The method according to claim 1, wherein thehydrosilylation-curable silicone composition comprises (A′) a siliconeresin having the formula (R¹R⁵ ₂SiO_(1/2))_(w) (R⁵₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z) (III); (B′) anorganosilicon compound having an average of at least two silicon-bondedalkenyl groups per molecule in an amount sufficient to cure the siliconeresin; (C) a catalytic amount of a photoactivated hydrosilylationcatalyst; and (D) a silicone rubber having a formula selected from (i)R¹R² ₂SiO(R² ₂SiO)_(a)SiR² ₂R¹ (IV) and (ii) R⁵R¹ ₂SiO(R¹R⁵SiO)_(b)SiR¹₂R⁵ (V); wherein R¹ is C₁ to C₁₀ hydrocarbyl or C₁ to C₁₀halogen-substituted hydrocarbyl, both free of aliphatic unsaturation, R²is R¹ or alkenyl, R⁵ is R¹ or —H, subscripts a an b each have a value offrom 1 to 4, w is from 0 to 0.8, x is from 0 to 0.6, y is from 0 to0.99, z is from 0 to 0.35, w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99,and w+x/(w+x+y+z) is from 0.01 to 0.8, provided the silicone resin andthe silicone rubber (D)(ii) each have an average of at least twosilicon-bonded hydrogen atoms per molecule, the silicone rubber (D)(i)has an average of at least two silicon-bonded alkenyl groups permolecule, and the mole ratio of silicon-bonded alkenyl groups orsilicon-bonded hydrogen atoms in the silicone rubber (D) tosilicon-bonded hydrogen atoms in the silicone resin (A′) is from 0.01 to0.5.
 6. The method according to claim 1, wherein thehydrosilylation-curable silicone composition comprises (A″) arubber-modified silicone resin prepared by reacting a silicone resinhaving the formula (R¹R² ₂SiO_(1/2))_(w)(R²₂SiO_(2/2))_(x)(R¹SiO_(3/2))_(y)(SiO_(4/2))_(z) (I) and a siliconerubber having the formula R⁵R¹ ₂SiO(R¹R⁵SiO)_(c)SiR¹ ₂R⁵ (VI) in thepresence of a hydrosilylation catalyst and, optionally, an organicsolvent to form a soluble reaction product, wherein R¹ is C₁ to C₁₀hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both free ofaliphatic unsaturation, R² is R¹ or alkenyl, R⁵ is R¹ or —H, subscript chas a value of from greater than 4 to 1,000, w is from 0 to 0.8, x isfrom 0 to 0.6, y is from 0 to 0.99, z is from 0 to 0.35, w+x+y+z=1,y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from 0.01 to0.8, provided the silicone resin (I) has an average of at least twosilicon-bonded alkenyl groups per molecule, the silicone rubber (VI) hasan average of at least two silicon-bonded hydrogen atoms per molecule,and the mole ratio of silicon-bonded hydrogen atoms in the siliconerubber (VI) to silicon-bonded alkenyl groups in silicone resin (I) isfrom 0.01 to 0.5; (B) an organosilicon compound having an average of atleast two silicon-bonded hydrogen atoms per molecule in an amountsufficient to cure the rubber-modified silicone resin; and (C) acatalytic amount of a photactivated hydrosilylation catalyst.
 7. Themethod according to claim 1, wherein the hydrosilylation-curablesilicone composition comprises (A′″) a rubber-modified silicone resinprepared by reacting a silicone resin having the formula (R¹R⁵₂SiO_(1/2))_(w)(R⁵ ₂SiO_(2/2))_(x)(R⁵SiO_(3/2))_(y)(SiO_(4/2))_(z) (III)and a silicone rubber having the formula R¹R² ₂SiO (R² ₂SiO)_(d)SiR² ₂R¹(VII) in the presence of a hydrosilylation catalyst and, optionally, anorganic solvent to form a soluble reaction product, wherein R¹ is C₁ toC₁₀ hydrocarbyl or C₁ to C₁₀ halogen-substituted hydrocarbyl, both freeof aliphatic unsaturation, R² is R¹ or alkenyl, R⁵ is R¹ or —H,subscript d has a value of from greater than 4 to 1,000, w is from 0 to0.8, x is from 0 to 0.6, y is from 0 to 0.99, z is from 0 to 0.35,w+x+y+z=1, y+z/(w+x+y+z) is from 0.2 to 0.99, and w+x/(w+x+y+z) is from0.01 to 0.8, provided the silicone resin (III) has an average of atleast two silicon-bonded hydrogen atoms per molecule, the siliconerubber (VII) has an average of at least two silicon-bonded alkenylgroups per molecule, and the mole ratio of silicon-bonded alkenyl groupsin the silicone rubber (VII) to silicon-bonded hydrogen atoms in thesilicone resin (III) is from 0.01 to 0.5; (B′) an organosilicon compoundhaving an average of at least two silicon-bonded alkenyl groups permolecule in an amount sufficient to cure the rubber-modified siliconeresin; and (C) a catalytic amount of a photoactivated hydrosilylationcatalyst.
 8. (canceled)
 9. The method according to claim 1, furthercomprising forming a coating on at least a portion of the silicone resinfilm.
 10. The method according to claim 9, wherein the coating is acured silicone resin.
 11. A silicone resin film prepared according tothe methods of claims 1 or 9.